>
> "Grimm et al also showed one more step from there. If the dichromated
> PVA does not contain certain amount of moisture, this PVA-Cr(III)
> complex undergoes further photosensitive reaction, which loses water
> and chromium drops out of the PVA complex and renders the PVA soluble
> again. This, they say agrees with the experience from phosphor coating of
> color CRT's, but also seems to agree with some of the careful gum printers
> in this list talking about moisture level in the coated layer during
> exposure."
>
There have been a great many things said on this list about moisture and
gum printing, some useful, many not. I responded to the above from what
I think is probably the best information extant about gum and moisture.
But what I think by no means enjoys a consensus here. When the unnamed
respondent says "this also seems to agree with some of the careful gum
printers in this list talking about moisture level in the coated layer"
there is no way of knowing which of the many contradictory statements
made here he is referring to, but try as I might, I can't think of any
statements made here on the topic that would agree with the idea that a
coating that's too dry will redissolve after hardening. But perhaps we
could have a more intelligent conversation about this if I knew which
statements by careful gum printers were being referred to.
Katharine Thayer
Received on Mon May 17 17:24:40 2004
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